That is a very interesting question.I have seen many accounts of people being sensitive to chinchilla dust. The industry standard seems to be Blue Cloud chinchilla dust. It comes from a pumice mine in California. When working with dust the biggest potential problem is exposure to silicates which stays in the lungs and causes a chain reaction that can result in COPD.
On the internet some claim Blue Cloud has no silicates in it, which is strange, since others describe it as being aluminum silicate powder. Some say there are no "free silicates". Not sure what that's supposed to mean. These claims all sound like malarchy to me. Pure aluminum silicate powder has an interesting MSDS and appears to be very harmful to breathe. I would be interested in seeing what the label actually says on the product.
As far as being a lung irritant that is certainly possible to both humans and chins when they are sick. If you have asthma or COPD It's best to avoid or minimize exposure. It would be the same for anyone living near a volcano. If volcanic ash was that bad it seems the dust from it years later would cause a worldwide epidemic of silicosis. Exposure to concentrated smoke is another story. PAH's in the smoke can wreak havoc with endothelial cells' DNA with each exposure.
Considering it's been 200 years and there is no known trend of silicosis in the chinchilla industry I don't think it's the dust you should be worried about.